Mechanical vacuum pump



arch 1, 1966 J. A. LE BLANC, JR 3,237,851

MECHANICAL VACUUM PUMP Filed July 22, 1964 a Sheets-Sheet 1 INVENTOR.

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United States Patent C) 3,237,851 MECHANICAL VACUUM PUMP Joseph Alexander Le Blane, In, Chicago, Ill., assignor to Cenco Instruments Corporation, Chicago, Ill., a corporation of Delaware Filed July 22, 1954, Ser. No. 384,298 8 Claims. (Cl. 230153) This invention relates generally to high vacuum mechanical pumping apparatus and more particularly, relates to important improvements in a mechanical vacuum pump of the rotary, oil sealed internal vane type.

The embodiment of the invention described and illustrated is a multiple-stage mechanical pump having an intake and an exhaust stage retained in a pump housing completely immersed in a suitable oil. Each stage has an internal pumping chamber provided in a stator which is swept by a pair of vanes resiliently mounted at diametrically opposed locations on a generally cylindrical member referred to as a rotor. The rotor is both rotatably and eccentrically mounted in the stator on a shaft coupled to a drive source, such as a motor, exterior of the pump housing. The intake stage of the pump is to be connected to the work space to be evacuated, so that the evacuated gases introduced into the pump are absorbed and/or occluded by the oil in the pumping chamber of the intake stage. This oil in the pump serves as a carrier for moving the evacuated gases from the intake stage to the exhaust stage and thence, out of the pump through the exhaust port of the pump. Further, the oil serves to effect vacuum tight sealing of the various stages and to lubricate moving parts. Notably then, an important consideration in pumps of this general character is the oil circulation system through the pumping chambers, the oil circulation system also required to cooperate with the gas circulation system for proper functioning of the pump. This invention is concerned with improvements in such circulation systems of a mechanical vacuum pump of the character described so that the following important advantages are realized:

(1) Elficiency of pump operation by degassing of oil to an effective degree heretofore not realized.

(2) Easier starting of the pump after being idle under vacuum and when the stages are filled with oil.

(3) More effective sealing of the stages and more effective lubrication of moving parts.

(4) Increased pump capacity without undue increase in pump size.

Accordingly, the primary object of the herein invention is to provide a high vacuum mechanical pump of the character described which can accomplish all of the foregoing advantages as well as other important advantages which will be elaborated upon during the full disclosure of the invention.

An important object of the invention is to provide novel means for degassing oil in such a pump so that a large throughput is realized after start of pump operation. Throughput refers to quantity of gas per unit of time moved through pump.

Another object of the invention is to provide a mechanical vacuum pump of the character described having a novel circulation system or path for the oil which includes hollow rotors in the several stages of the pump having their internal cavities communicating one with the other in an uninterrupted path for said oil from between the end plate of the intake stage to the end plate of the exhaust stage of the pump, said hollow rotors causing more effective degassing of oil and positive sealing of the stages while permitting less critical dimensioning between the vanes and the opposed surfaces of the stator of each stage and better lubrication of moving parts of the stages.

Patented Mar. '1', 1966 Another important object of the invention is to provide a vacuum pump of the character described in which novel means are provided for degassing of the oil both immediately upon entry of the oil into the exhaust stage at starting of the pump and at all times prior to feeding of oil to the intake stage from the exhaust stage such that the lubrication and sealing of the stages during operation of the pump is achieved only with degassed oil.

Another object of the invention is to provide a vacuum pump of the character described having an internal chamber in addition to and communicating with the pumping chambers of the intake and exhaust stages respectively for receiving said oil, said additional internal chamber enabling advantageous degassing of the oil heretofore unobtainable in pumps of this general type, including means provided in said additional chamber for forcing said oil by centrifugal forces applied thereto during operation of the pump to lubricate the moving parts of the stages and maintain an effective seal of the stages only with degassed oil.

Additional objects of the invention are to provide a mechanical vacuum pump of the character described having a novel dual action exhaust valve assembly mounted in association with the discharge port of the exhaust stage for better operation of the pump; a pump which is fabricated from a reduced number of parts and with interchangeable parts which can reduce and/or eliminate expensive and complicated machining operations employed in prior pump parts and enable assembly of additional stages for varying the capacity of the pump without corresponding increase in size; in which the rotary vanes of the stages are mounted to extend through the drive shaft of the pump for improved pump capacity to size ratio relationship; and which is sturdy and more efficient in its operation without corresponding increase in cost and size of the pump.

The foregoing and other objects of the invention will become apparent as the description thereof evolves in which a preferred embodiment has been described in detail in the specification and illustrated in the accompanying drawings. It is contemplated that minor variations in the size, arrangement, construction and proportions of the several parts of the invention may occur to the skilled artisan without departing from the scope or sacrificing any of the advantages thereof.

In the drawings wherein the same reference characters have been employed to identify identical or equivalent parts throughout the several figures thereof:

FIG. 1 is an exploded perspective view of the mechanical vacuum pump embodying the invention showing the component parts thereof.

FIG. 2 is a vertical sectional view taken through said pump along a plane parallel to the longitudinal axis of the pump.

FIG. 3 is a sectional view taken through said pump along the line 33 of FIG. 2 and in the direction indicated generally.

FIG. 4 is a fragmentary sectional view taken through the pump along the line 44 of FIG. 2 and in the direction indicated generally.

FIG. 5 .is a fragmentary end view taken from along the line 5-5 in FIG. 2 and in the direction indicated generally.

FIG. 6 is a fragmentary sectional view taken along the line 6-6 of FIG. 4 and in the direction indicated generally, portions being broken away to show structural details.

FIG. 7 is a perspective view of the main body member of said pump with the rotor assembled therein to provide the intake stage of the pump.

FIG. 8 is a perspective view of the stator and rotor assembled to form the exhaust stage of the pump.

FIG. 9 is a plan view of one of the novel hollow rotors with portions in section to show details.

FIG. 10 is a fragmentary sectional view taken along the line 1010 of FIG. 2 and in the direction indicated generally.

FIG. 11 is an exploded view of a rotor assembly including the vanes resiliently mounted thereon and extending through the drive shaft on which the rotor is keyed.

FIG. 12 is a sectional view taken through the intake and exhaust stator and rotor assemblies thereof respectively along a plane parallel to the drive shaft of the pump, such as along line 1212 in FIG. 2.

Referring to the drawings, in FIGS. 1 and 2, the mechanical pump embodying the invention is identified generally by the reference character 20. As is common in the trade, the size, capacity, ultimate vacuum and other specifications for a vacuum pump of this general type may vary between models of the manufacturer and as dictated in part by the requirements of the pump in a particular application. Consequently, a recitation of dimensions of parts will not be necessary for purposes of understanding the invent-ion. Pump 20 represents a two-stage mechanical vacuum pump, although additional stages can be incorporated thereinto with important advantages engendered by the herein invention. As identified generally in FIG. 2, there is an intake stage 22 and an exhaust stage 24 assembled in face abutting relationship with and on opposite sides of a center or coupling plate 26. The working parts of the intake stage 22 include a cast metal main body member 27 to which is secured the intake housing assembly 28 for closing off the intake stage end of the pump and the exhaust housing assembly 29 for closing off the exhaust stage end of the pump. Each of said housing assemblies is a suitably dimensioned, dish-shaped metal member for encasing the working parts of the stage of the pump with which it is associated. Each housing assembly is installed by means of a plurality of bolts 30 engaged through circumferentially spaced apart openings in the peripheral flange 31 on each housing assembly which are aligned with respective holes in the main body member 27. When mounted, the housing assemblies provide a volume of space 32 around the stages 22 and 24 which is filled with oil, said space 32 and the working components of the pump thereby being sealed off from ambient atmosphere.

The working parts of the stages are driven by means of a common shaft 33 having a slotted end 34 protruding outwardly of the exhaust housing assembly 29 through a bearing 35. Said end 34 is adapted to mount a pulley wheel (not shown) for coupling the shaft to a suitable source of power, such as a motor, for driving said shaft. A gas ballast supply tube 36 of conventional construction is shown operatively associated with the exhaust stage 24 through the main body member 27 for introducing air in small amounts at atmospheric pressure, this component being optional insofar as the invention herein is concerned.

Main body member 27 is an integral cast metal member of hollow, generally rectangular configuration and provides the intake stage stator and intake port for the pump. As seen in FIGS. 1, 3 and 7, the body member 27 has a base portion 37 which can be provided with outwardly extending perforated flanges 38 for anchoring the pump on a flat surface. In the alternative, said base can be provided with depending ribs 39 (FIG. 2) for supporting the pump on such a surface. Upstanding from opposite ends of the base 37 is a pair of spaced apart side walls 40 which are connected across their upper extremeties by the top wall 41 which is gene-rally parallel to the base. Thus, base 37, side walls 40' and wall 41 cooperate to define an outer shell or frame 42 having oppositely directed end faces 43 and 44 which are fiat and vertically oriented in planes normal to the base 37, as seen in FIG. '2. In the operating disposition of said member 27, the flat end face 43 faces toward the exhaust stage 24 and the end face 44 faces away from the exhaust stage 24 of the pump.

Inside the outer shell or frame 42 is a second shell 45 which is smaller than said frame 42 and connected thereto by the webs or struts 46 at a plurality of locations therearound. The spaces 46a between shells 42 and 45 extend entirely through the body 27 and form part of the space 32 for immersing the stage in oil. The top wall 41 and the thickened upper end wall 45a of said shell 45 are connected by the hollow block formation 47 offset inwardly from end face 43. The shell part 45 has an enlarged cylindrical cavity 48 extending entirely through the same to said opposite flat faces 43 and 44 of the body member 27. Thus, the shell formation 45 comprises a stator on the interior of the main body member 27 and will be referred to hereinafter as the stator 45.

The main body member 27 comprises the intake stage of the pump. The top wall 41 has an intake port 49 which communicates with the bore 49a extending entirely through the formation 47 into cavity 48 of the stator 45. The shaft 33 extends through the cavity 48 and keyed on the shaft is a rotor 50 carrying the diametrically opposed resiliently mounted vanes 52 and 53. The vanes 52 and 53 normally are spring-biased into contact with the internal circumferential surface of the cavity 48. The rotor 50 has a generally cylindrical configuration and is formed preferably as a cast metal member. Notably, the rotor is hollow throughout its axial length for purposes described in detail subsequently herein. The rotor is mounted on the shaft 33 eccentrically within the circular cavity 48 so that there is provided a crescent-shaped pumping chamber 54 between the outside circumference of the hollow rotor 50 and the inside circumference of the stator 45.

The rotor 50 has a cylindrical outer wall 55 from the interior circumferential surface of which extend the bosses 56 facing one toward the other. Supported by said bosses 56 is a spider formation 57 having at its center the hollow, cylindrical sleeve 58 coaxial with the wall 55. The shaft 33 extends through the sleeve 58 and is keyed thereto as indicated at 60 in suitable registered slots 61 in the shaft and sleeve. There is a radially extending slot 62 extending from the interior of sleeve 58 through each boss 56 and opening to the exterior circumference of the wall 55. Each vane 52 and 53 respectively is accommodated in one of said slots 62. Thus, the rotor 50 is hollow and has a through passage-i way axially therethrough.

Referring to FIG. 11, the vanes 52 and 53 are identical so that a description of one will suflice. The vane 52 is a fiat metal member of generally T-shaped configura-- tion. The cross-head portion 64 has the portion which is biased into engagement with the interior circumference of the stator 45. The second leg 65 is a pair of sockets 66 opening to the end face thereof for receiving the pins 67. In assembly, the vanes are arranged with their legs 65 spaced apart and aligned one with the other and the ends of the pins 67 are engaged in the sockets 66. A coil spring 68 is engaged around each pin 67 with the ends of the springs abutting the end faces of the legs 65 so as normally to spring-bias the vanes 52 and 53 in opposite directions one relative to the other into engagement with the stator.

Shaft 33 has a slot 70 entirely through and along a diameter thereof. The width and breadth of the slot is selected so as to slidingly accommodate the leg 65 of a vane therethrough. As seen in FIG. 11, the slot 70 is located between the keyway slots 61 for securing the: rotor 50 on the shaft 33 at key juncture 60. As seen in FIG. 10, the vane 52 has its leg portion 65 extending through the slot 70 in the shaft and as the rotor 50 rotates, the vane 52 also will be moved inwardly into the shaft 33 at the corresponding point in the pumping cycle. By providing the slot 70 which can accommodate the vanes 52 and 53 therein alternately during the pumping cycle, it is possible to increase the capacity of the pump without unduly increasing the size of the chamber to be pumped and hence, the overall size of the pump,

The vanes are permitted a greater length of travel thereby increasing the volume swept by the vanes. Also, the hollow character of the rotor is maintained.

The intake port 49 communicates with the crescent shaped pumping chamber 54 of the intake stator 45, as seen in FIG. 3, through the bore 49:: in block formation 47. The chamber 54 also has an exhaust port 72 which connects with a cross-over passageway 74 at one end 76 thereof. The passage 74 opens at 78 to the end face 43, it being prevented from opening to the opposite end face 44 by the formation 47. However, the end 76 of said passageway 74 also opens to a passageway 89 which extends entirely through the body member 27 to one side of block 47. Note that exhaust port 72 from the intake chamber 54 also communicates with the through passageway 80 in the member 27.

As seen in FIGS. 1 and 2 the pumping chamber 54 of the intake stage is closed off by the coupling plate 26 and an intake stage end plate designated 82. The end plate 82 is a metal plate having an elongated hole 84 therethrough adjacent one upper corner of the plate. This hole 84 communicates with the passageway 81) through the main body member 27. Mounted on the exterior face of the plate 82 is a flat metal valve member 86 which is suspended from bracket 87 to hang free overlying the opening 84. The opening 84 serves as a relief opening into space 32 from the interior of the intake stage 22 to assist in starting the pump after it has been idle under vacuum and suddenly opened to the work space to be evacuated. This enables use of a motor drive for shaft 33 of lesser horsepower. The coupling plate 26 has an elongated opening 88 in one upper corner thereof which aligns with the opening 78. The second upper corner of the plate 26 is imperforate so as to block off the open end of the passageway 80 through the main body 27 facing toward the exhaust stage. Passageway 84 is aligned with the opposite open end of passageway 80.

Referring to FIG. 8, the pumping chamber of the exhaust stage is designated 90. It is crescent-shaped and provided between the internal circumference of a separate stator 92 and the outside circumference of rotor 93. The rotor 93 is identical to the rotor 50; it is eccentrically mounted in the pumping chamber 90 of the exhaust stator 92 on the shaft 33. It also has springbiased vanes 52 and 53 which sweep the pumping chamber 90 of the exhaust stator. As seen in FIG. 8, the vanes will be rotated in a counter-clockwise direction for pumping the chamber 90 through the exhaust port 94. The intake port of the stator 92 is shown at 95 connecting with passageway 95a into chamber 90. As seen in FIG. 4, there is a double-flutter valve 96 mounted across the exhaust port 94. Note that port 95 is part of a through passageway in the upper right hand corner of the stator.

In FIG. 2, the exhaust stator 92 with its rotor 93 is shown on the left of the main body and abutting the coupling plate 26 to close one end of the exhaust stage. The coupling plate 26 has an opening 19!) which accommodates a bushing 102 for the shaft 33 therethrough. There are ducts 104 entirely through the coupling plate which communicate between the exhaust stage rotor and intake stage rotor as best seen in FIG. 1. Also, the coupling plate 26 has the opening or inlet port 88 in registry with exhaust opening 78 in the intake stator so that port 106 is the inlet to the exhaust stage pumping chamber 90 from the intake stage. The circulation system or path for the intake of air, shown by arrows in FIG. 1, is from the work space to be evacuated through the port 49 and bore 490 into the intake pumping chamber 54, through the exhaust port 72 of the intake pumping chamber into passageway 80, through the cross-over 74 into the opening 78, through the intake or inlet port 166 in the coupling plate into the pumping chamber 90 of the exhaust stator 92 through passages 95 and 95a.

d The chamber is pumped out by the rotor 93 and its vanes 52 and 53 through the exhaust port 94 controlled by the double flutter vale 96.

Referring to FIGS. 1 and 2, mounted to the end of the exhaust stator 92 is the exhaust end plate 110 and to the outer face of the exhaust end plate 110 is the exhaust end cap 112. The inside face of the exhaust end cap 112 is hollowed to provide an enlarged vertically oriented passageway 114 between the exhaust end plate 110 and the exhaust end cap 112. In the upper wall of the end cap 112 is an oil intake hole 116 which is enlarged and conveniently fitted with a split pin 118. The exhaust end plate 110 has the shaft 33 journalled therein in a suitable bushing 119 and there is a pair of passageways 120 in the exhaust end plate 110 which communicates between the passageway 114 and the interior of the exhaust stage stator and rotor assemblage.

The intake stage end plate 82 also mounts an intake end cap 122 which is identical to the end cap 112 with the exception that it does not have the oil intake hole 116 in the top wall thereof. The intake end plate 82 has a suitable journal 124 for the inside end of the shaft 33 and there are the passageways 126 communicating between t-he end cap 122 and the interior of the intake stage.

Referring to FIGS. 1 and 4, the exhaust end plate 110 also has a passageway 84' across which is installed the relief valve plate 86. Note that passageway 84' also aligns with passageway 95. As appears from the drawings, it will be appreciated that the intake end plate and the exhaust end plate both have the bypass ports and valves opening outwardly into the space 32 between the stators and the housing assemblies, this best being seen in connection with the relief valve 86 shown in FIG. 2.

Consider now the circulation of the oil through the pump, it being understood that the pump housing is filled with a desirable grade machine oil. The oil enters through the oil intake opening 116 into the passageway 114 of the exhaust end cap 112. The path of the oil is shown by arrows in FIG. 2. The oil travels down the path or passageways 116 through the passageway 120 into the exhaust stage stator-rotor assembly. The oil passes centrally through the hollow rotor of the exhaust stage, the pumping chamber 90, passes through the passageway 88 in the coupling plate 26 into the intake stage, through the hollow rotor of the intake stage into the passageways 126 and filling the intake end cap 122. When the pump is started from a vacuum, the oil entering through the opening 116 is immediately degassed because of the vacuum condition on the interior of the pump and spreading of oil on the inside surface of the hollow rotor of the exhaust stage. Notably, the oil enters the exhaust stage and for degassing of the oil, there is provided in addition a slot 13% (FIG. 4) which is on the face 132 of the coupling plate facing into the exhaust stage. The slot or groove 130 is vertically arranged and communicates at its bottom end 132 with the pumping chamber 90 and the inside of the exhaust stage rotor 93. At its upper end, the slot 130 connects with the inlet port 88 in the coupling plate 26 which communicates with the pumping chamber 90 of the exhaust stage. Notably, this inlet opening 88 in the coupling plate 26 also communicated with the exhaust passageway 78 from the intake stage. Thus, the gas from the oil is carried into the fiow of air and oil from the intake stage to the exhaust stage of the pump from port 78. In no case is any oil that is not degassed distributed or introduced to the intake stage of the pump.

As the pump rotates, the oil on the interior of the rotors is thrown outwardly by centrifugal force and into the clearance space between the sides of the vanes and the adjacent surfaces of the stator. The violent centrifugal action fills the clearance spaces between the vanes and the adjacent stator, causing a seal of the various stages which is much more effective than the prior art. Further, this centrifugal action eliminates the need for vset the bias of the coil springs on the plate 140.

critical dimensioning between the vanes and the stator walls. The centrifugal action throwing the degassed oil outwardly fill-s these spaces regardless of their dimension and serves to lubricate the stages. Notable, further, is that the oil is degassed immediately upon entering into the vacuum of the interior of the pump through the oil intake opening 116 in the exhaust end cap 112. Degassing is further augmented by virtue of spreading of oil on exterior surfaces of the rotor and stator by centrifugal force due to the hollow rotor structure.

Thus, it may be seen that the exhaust stage pumps not only the intake stage but also pumps a third chamber which is the space provided by the hollow rotors of the stages and into which oil is allowed to flow and return and in turn become degassed. Notably, then, only degassed oil is used for lubrication and for maintaining a seal of the stages in the pump. The centrifugal force exerted by the hollow rotors on the oil achieves more positive seal and allows for parts to be less critical, especially between the vanes and the stator walls.

The pump is easier to start for other reasons. The suitably valved relief openings in the end plates are enabled to burst open under the initial surge of the pump relieving the pressure on the interior thereof so as to enable the pump to start. These relief valves are 86 and 86' respectively and so when the stages are filled with oil, upon starting the pump, the valves burst open when the pressure within the pump exceeds 15 pounds per square inch therefore allowing the oil to escape from the interior of the pump without having to be circulated through the exhaust stage first. This allows the pump to be started after being idle under vacuum, a condition which was not obtained satisfactorily with prior art pumps.

We now examine the double flutter valve 96 which covers the large exhaust port 94 of the exhaust stage, which, notably, is a relatively large cross-section exhaust port. The valve 96 is a double purpose exhaust valve, it being made of two parts. One part is a spring loaded heavy plate/140 which covers or spans the exhaust port 94 which may cover a two inch diameter hole. This plate 140 opens when large quantities of air and oil are being exhausted, a condition occurring usually at starting of the pump. There is a pair of smaller openings 142 in plate 14 which are valved by the smaller spring steel leaf valve 144 secured by bolt 146 on top of plate 140.

The valve is mounted overlying the port 94 by means of the long bolts 148 threaded at their ends into the casting of stator 92. The bolts also pass through the plate 140. Surrounding each bolt 148 is a heavy coil spring 150 which bears at one end thereof against the plate 140 and at its opposite end against the metal bracket 152. The opposite ends 154 of the bolts pass through the bracket 152 and receiving the nuts 156 for holding the bracket 152 against the springs 150. The bracket 152 has a leg segment 154 bent to extend against the stator 92 to limit the extent of movement of bracket toward this stator. This serves to The action of the valve 94 further is noteworthy in that the upper surface of the exhaust stator having the exhaust port is canted at approximately a 25 degree angle. The exhaust material from the exhaust pumping chamber 90 is cleared from the exhaust stator and is not allowed to drip back into the exhaust pumping chamber at any time. This is a concept which enables positive throwing out of I oil and air from the exhaust pumping chamber at all times.

. openings in the component parts. Referring to FIG. 1,

it will be seen that the coupling plate 26 has the perforated ears 158 which can accommodate bolts 160 to engage in the openings 162 in stator formation 45 for coupling the coupling plate and main body 27 in abutting relationship. Also the coupling plate 26, end plates 82 and and exhaust stator 92 have the open ear formations, such as 164, for accommodating long bolts. The stator 92 also has the passageways 166 for coupling the stator to the main body 27 by bolts engaged through said passageways 166 into holes 168. In view of the illustration of the pump parts in FIG. 1 in their consecutive order of assembly, the exact alignment of such openings, ears, etc. should be manifestly clear without further detailed analysis.

Although not specifically shown, the size of the pump embodying the invention can be varied easily and economically. For instance, the main body 27 can be used alone, with suitable end plates for a single stage pump. To increase the pump size, additional main bodies as desired can be keyed to suitably dimensioned shaft 33 for sideby-side operation and the same applies in connection with the exhaust stator body 92. However, one of the distinctive advantages of the invention in this regard is that the capacity of the pump can be increased without unduly increasing the size of the pump proportionally. This is due to the manner of mounting the vanes 52 and 53 for movement through the shaft 33. This allows greater distance of travel for the vanes, i.e., the additional diameter of the shaft 33, thereby increasing the volume of space swept by the vanes.

Notably, the pump embodying the invention is constructed of many interchangeable parts. The end plates, end caps, rotors and vanes, for instance, are interchangeable. An end plate can be machined to function as the coupling plate by adding the groove 130. The pump parts can be cast directly incorporating the various parts, ducts, and holes in the casting design to reduce and/or eliminate costly machining operations.

In conclusion, it can be noted that the improved degassing of oil in the pump contributes to the materially improved efiiciency of the pump. The faster degassing features discussed provides for materially improved throughput and conductance for the pump than heretofore obtained. Because of such faster and more effective degassing, the pump is able to accommodate greater quantities of gas from the work space to be evacuated at the early pumping stages. This results in greater quantities of gas being evacuated after pumping is commenced because greater conductance for the pump is realized. Also, improved conductance between the intake and exhaust stages of the pump is contributed by passages 46a in main body 26.

It is believed that the invention has been described in suflicient detail to enable the skilled artisan to understand and practice the same. The invention has been particularly pointed out in the appended claims in language intended to be broadly construed commensurate with the progress in the arts and sciences contributed therebyj What it is desired to secure by Letters Patent is:

1. A mechanical vacuum pump of the rotary, oil sealed internal vane type which includes at least one intake stage and one exhaust stage assembled in abutting relationship with and on opposite sides of a coupling plate and each stage has an end plate for closing the stage at an end thereof opposite said coupling plate, said end plates having fluid passageways therethrough, a housing assembly enclosing each stage and providing a volume of space surrounding said stages for retaining the same immersed in an oil, a drive shaft extending through said stages, each stage having a stator and a substantially hollow rotor mounted on the shaft in cooperation one with the other to provide a pumping chamber for the stage, said rotors each mounting radially movable, spring-biased vanes for sweeping the pumping chamber upon driving of the shaft, and continuous fluid circulation conduit means for said oil extending between said end plates and axially through the interior of said rotors, and through said passageways into said space, said coupling plate having oil degassing means along the face thereof communieating with the conduit means and pumping chamber of said exhaust stage,

2. A pump as described in claim 1 in which said degassing means comprises a groove connection between the interior of the exhaust stage rotor and pumping chamber and the intake port of the exhaust stage, said coupling plate having said exhaust stage intake port.

3. A pump as described in claim 2 in which said vanes of each rotor are radially movable through said shaft.

4. A mechanical vacuum pump of the rotary, oil sealed internal vane type which includes at least one intake stage and one exhaust stage assembled in abutting relationship with and on opposite sides of a coupling plate and each stage has an end plate for closing the stage at an end thereof opposite said coupling plate, said end plates having fluid passageways therethrough, a housing assembly enclosing each stage and providing a volume of space surrounding said stages for retaining the same immersed in an oil, a drive shaft extending through said stages, each stage having a stator and a substantially hollow rotor mounted on the shaft in cooperation one with the other to provide a pumping chamber for the stage, said rotors each mounting radially movable, spring-biased vanes for sweeping the pumping chamber upon driving of the shaft, and continuous fluid circulation conduit means for said oil extending between said end plates and axially through the interior of said rotors, and through said passageways into said space, each end plate having relief valve means for connecting the interior stage adjacent thereto and said space for facilitating starting of the pump without requiring prior oil circulation through the exhaust stage.

5. A pump as described in claim 4 in which said valve means comprises a flat metal plate freely suspended on the exterior face of the end plate and movable to open the valve when internal pump pressure exceeds a prede termined value.

6. A mechanical vacuum pump of the rotary, oil sealed internal vane type which includes at least one intake stage and one exhaust stage assembled in abutting relationship with and on opposite sides of a coupling plate and each stage has an end plate for closing the stage at an end thereof opposite said coupling plate, said end plates having fluid passageways therethrough, a housing assembly enclosing each stage and providing a volume of space surrounding said stages for retaining the same immersed in an oil, a drive shaft extending through said stages, each stage having a stator and a substantially hollow rotor mounted on the shaft in cooperation one with the other to provide a pumping chamber for the stage, said rotors each mounting radially movable, spring-biased vanes for sweeping the pumping chamber upon driving of the shaft, and continuous fluid circulation conduit means for said oil extending between said end plates and axially through the interior of said rotors, and through said passageways into said space, said coupling plate being vertically oriented and having opposite flat faces, a passageway transversely therethrough adjacent an upper corner thereof providing the intake port for the exhaust stage and exhaust port for the intake stage, and degassing means on the surface of said coupling plate facing the exhaust stage and communicating between said passageway and the rotor and chamber of said exhaust stage.

7. A mechanical vacuum pump of the rotary, oil sealed internal vane type which includes at least one intake stage and one exhaust stage assembled in abutting relationship with and on opposite sides of a coupling plate and each stage has an end plate for closing the stage at an end thereof opposite said coupling plate, said end plates having fluid passageways therethrough, a housing assembly enclosing each stage and providing a volume of space surrounding said stages for retaining the same immersed in an oil, a drive shaft extending through said stages, each stage having a stator and a substantially hollow rotor mounted on the shaft in cooperation one with the other to provide a pumping chamber for the stage, said rotors each mounting radially movable, spring-biased vanes for sweeping the pumping chamber upon driving of the shaft, and continuous fluid circulation conduit means for said oil extending between said end plates and axially through the interior of said rotors, and through said passageways into said space, said exhaust stage end plate having a hollow end cap secured to the outside face thereof, said cap communicating between the exhaust stage rotor and said space through said exhaust stage end plate.

8. A mechanical vacuum pump of the rotary, oil sealed internal vane type which includes at least one intake stage and one exhaust stage assembled in abutting relationship with and on opposite sides of a coupling plate and each stage has an end plate for closing the stage at an end thereof opposite said coupling plate, said end plates having fluid passageways therethrough, a housing assembly enclosing each stage and providing a volume of space surrounding said stages for retaining the same immersed in an oil, a drive shaft extending through said stages, each stage having a stator and a substantially hollow rotor mounted on the shaft in cooperation one with the other to provide a pumping chamber for the stage, said rotors each mounting radially movable, spring-biased vanes for sweeping the pumping chamber upon driving of the shaft, and continuous fluid circulation conduit means for said oil extending between said end plates and axially through the interior of said rotors, and through said passageways into said space, said intake stage including an integral metal body having the intake stage rotor therein to provide the intake stage stator for the pump, said housing assemblies being secured to said body.

References Cited by the Examiner UNITED STATES PATENTS 901,539 10/1908 Leyner 230-153 X 1,616,733 2/1927 Wood 230-210 X 1,675,686 7/1928 Barnes 230153 2,877,946 3/1959 Garrison et al 230153 ROBERT M. WALKER, Primary Examiner. 

1. A MECHANICAL VACUUM PUMP OF THE ROTARY, OIL SEALED INTERNAL VANE TYPE WHICH INCLUDES AT LEAST ONE INTAKE STAGE AND ONE EXHAUST STAGE ASSEMBLED IN ABUTTING RELATIONSHIP WITH AND ON OPPOSITE SIDES OF A COUPLING PLATE AND EACH STAGE HAS AN END PLATE FOR CLOSING THE STAGE AT AN END THEREOF OPPOSITE SAID COUPLING PLATE, SAID END PLATES HAVING FLUID PASSAGEWAYS THERETHROUGH, A HOUSING ASSEMBLY ENCLOSING EACH STAGE AND PROVIDING A VOLUME OF SPACE SURROUNDING SAID STAGES FOR RETAINING THE SAME IMMERSED IN AN OIL, A DRIVE SHAFT EXTENDING THROUGH SAID STAGES, EACH STAGES HAVING A STATOR AND A SUBSTANTIALLY HOLLOW ROTOR MOUNTED ON THE SHAFT IN COOPERATION ONE WITH THE OTHER TO PROVIDE A PUMPING CHAMBER FOR THE STAGE, SAID ROTORS EACH MOUNTING RADIALLY MOVABLE, SPRING-BIASED VANES FOR SWEEPING THE PUMPING CHAMBER UPON DRIVING OF THE SHAFT, AND CONTINUOUS FLUID CIRCULATION CONDUIT MEANS FOR SAID OIL EXTENDING BETWEEN SAID END PLATES AND AXIALLY THROUGH THE INTERIOR OF SAID ROTORS, AND THROUGH SAID PASSAGEWAYS INTO SAID SPACE, SAID COUPLING PLATE HAVING OIL DEGASSING MEANS ALONG THE FACE THEREOF COMMUNICATING WITH THE CONDUIT MEANS AND PUMPING CHAMBER OF SAID EXHAUST STAGE. 